New Environmental Protection Agency air-quality standards reduce the allowable size of particulates, or tiny particles in the air, and restrict the overall daily exposure of residents to wood and diesel soot by 50 percent, said Heather Marlow, city lands and resources manager.

Until recently the EPA allowed globules of pollution the size of common dust. New regulations reduce allowable particulate size by 75 percent.

No ban was in effect as of Friday. But during a cold snap in early December, the air pollution particulate count near Floyd Dryden Middle School surpassed EPA standards on several occasions, City Manager Rod Swope said.

"We started to see we were exceeding the standard," he said. "It got us thinking."

Any alert or emergency burn ban would only apply to the Mendenhall Valley from Fred Meyer to Auke Lake between Juneau International Airport and the Mendenhall Glacier.

The last woodstove burn bans came to Juneau in the early 1990s with previous tightening of EPA standards, Swope said.

Burn bans

 Areas between Fred Meyer and Auke Bay from the airport to the Mendenhall Glacier are subject to burn bans and advisories.

 If a woodstove is within the area of the ban, the city no longer allows some exemptions, as it did in the 1990s.

 Wood pellet stoves are exempt.

When certain weather conditions exist, the city will issue an alert, asking people to voluntarily halt use of their woodstoves, Marlow said.

During temperature inversions, the city could ban the use of all woodstoves in the Valley, and police would enforce the ban.

The trapped air phenomena known as an inversion typically follows a night when cold air collects in a valley bottom, like water in a sink, and stagnates under warmer air above.

Fritsch said the forecast through midday Monday shows the potential for an inversion to build.

If the city doesn't address pollution levels, it could face EPA fines and the possibility of a requirement by the federal government to develop a new air-quality compliance program, Swope said. The best way for the city to control air quality during inversions is to encourage people to stop using woodstoves during certain periods.

Building codes do not allow woodstoves to be the primary heat source for any home in the city, and no home within the ban area is exempt from the regulation, Marlow said.

Advisories and bans, when issued, should last three to five days, Swope said.

Enforcement of a ban is more complicated than it appears, Juneau police Sgt. Dave Campbell said. Officers on patrol have to deal with wood pellet stoves that are exempt, and black smoke could be the result of a poorly tuned oil furnace.

"Nothing says you can't have a dirty oil furnace, Campbell said.

But, if the city calls the emergency ban, officers will enforce the city's rules. Fines for the first violation will be $300 or less, second offenses are misdemeanors that draw the possibility of 90 days in jail and a $1,000 fine, Campbell said.